/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* @(#)s_ilogb.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/* ilogb(double x)
 * return the binary exponent of non-zero x
 * ilogb(0) = 0x80000001
 * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
 */

#ifdef POK_NEEDS_LIBMATH

#include "math_private.h"
#include <libm.h>

int ilogb(double x) {
  int32_t hx, lx, ix;

  GET_HIGH_WORD(hx, x);
  hx &= 0x7fffffff;
  if (hx < 0x00100000) {
    GET_LOW_WORD(lx, x);
    if ((hx | lx) == 0)
      return 0x80000001; /* ilogb(0) = 0x80000001 */
    else                 /* subnormal x */
        if (hx == 0) {
      for (ix = -1043; lx > 0; lx <<= 1)
        ix -= 1;
    } else {
      for (ix = -1022, hx <<= 11; hx > 0; hx <<= 1)
        ix -= 1;
    }
    return ix;
  } else if (hx < 0x7ff00000)
    return (hx >> 20) - 1023;
  else
    return 0x7fffffff;
}

#endif
